Definition

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Usage experts warn against confusing the verbs assay and essay. Some confusion shouldn't be surprising, since the two words look alike and derive from the same root, the Middle French essai, meaning "test" or "effort" (a root that, in turn, comes from the Late Latin exagium, meaning "act of weighing"). At one time, the two terms were synonyms, sharing the meaning "try" or "attempt," but many modern usage commentators recommend that you differentiate the two words, using essay when you mean "to try or attempt" (as in "he will essay a dramatic role for the first time") and assay to mean "to test or evaluate" (as in "the blood was assayed to detect the presence of the antibody").